I recently acquired an OEM 18” 338 LM conversion kit off of the EE. I finally made it out to the range to zero it and try it out but was having a hard time getting it on paper. Initially I had set my sights on the 100 yard targets as the glass was zeroed for the 308 barrel in there previously. But I had no luck, so I kept moving in closer until I finally found my issue. Bullets were keyholing fairly consistently at 50 yards. The rifle in question is a Desert Tech SRS A1, the 338 conversion is a Desert tech gen 2 barrel 1-9 twist with desert tech brake. The ammo used was Hornady Match 250gr BTHP (plain brown box). I saw no signs of baffle strikes, or crown damage etc, and I didn’t notice anything extraordinary about the fired brass, I slipped the neck over an unfired round and the brass didn’t appear to be over sized on the bullet, slipped over the bullet with very light resistance but wasn’t sloppy etc.. Most of the keyholes were sideways enough to make out the orientation of the bullet and seemed to point to the same general direction (at 50 yds) but I don’t know for sure that that was consistent. Could 1-9 be too much twist for a 250gr? I plan to get the rifle in to the professionals when I get a chance, but in the mean time, being completely new to the caliber, I thought it wouldn’t hurt to throw out a help request on here as I know many of you are quite knowledgeable on the subject. Any help would be greatly appreciated. Thanks in advance.
Having issues with my 338 LM, keyholing when attempting to zero. Enlighten me please
- Thread starter Uisge
- Start date
It’s marked as a 1-9.
It was used, It looks pretty good, to my eye. I just had another look to see if I could see anything. I wish I had some heavier bullets to try in it, just to see if it makes a difference. Possibly the short barrel and lighter bullets aren’t playing nice together.
I think if anything the lighter bullet will shoot better than a heavier one .
I suspect something is not right with the bore itself but without actually seeing it, it is hard to tell
Cay
I tend to agree with you, I guess the next step is to find a variety of different ammo and see what happens. There really doesn’t look like anything is wrong with the bore etc. Any suggestions?
1-9 should be fine with 250's. Mine was a 1-10 twist and stabilized 300's handily. - dan
New Camper
CGN frequent flyer
- Location
- Lurking in the woods near SFRC.
18" barrel? so realistically the actual bore length is going to be 18"-chamber length(at least 3.5")=14.5" barrel. Being a 338 LM you'll have a charge of something slow like IMR 7828 or Retumbo... I'm going to go with the twist rate is adequate but part of the stability formula is velocity: but instead of having the velocity you are having a majestic fireball.
The fireball is quite majestic! Perhaps a heavier bullet would consume a bit more before it erupts out of the brake? Anyone want to trade some Hornady 250gr BTHP for something a bit different?
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I think you better put a bore scope in that thing or at least slug the bore take the break off and check the crown for wear etc. take a unloaded billet and see if it wont just slide into the muzzle saw one once that was either expanded or worn from cleaning bullet went in 1/2 inch into the muzzle before it started to get snug in the rifling
redshooter
CGN Ultra frequent flyer
- Location
- Central Ontario
Factory stuff.
Did you sort this out yet?
There is no reason factory Hornady 250gr BTHP ammo should be keyholing at 50m. 1-10" or faster is enough twist in the barrel to stabilize it. According to JBM ballistics, the Miller stability factor for this bullet in a 1-10 twist barrel at 2750 fps is 2.1 or in other words, plenty fast enough twist.
Do you have a bore scope or access to one? It's just a guess but you may have been sold a shot out used barrel.
As others have also stated , the problem may also be a damaged crown or misaligned brake.
There is no reason factory Hornady 250gr BTHP ammo should be keyholing at 50m. 1-10" or faster is enough twist in the barrel to stabilize it. According to JBM ballistics, the Miller stability factor for this bullet in a 1-10 twist barrel at 2750 fps is 2.1 or in other words, plenty fast enough twist.
Do you have a bore scope or access to one? It's just a guess but you may have been sold a shot out used barrel.
As others have also stated , the problem may also be a damaged crown or misaligned brake.
If it truly is an A2 barrel, it will be fluted and have a 3 port brake on it from desert tech
I have an srs A2 chassis with the A1 18" barrel (non fluted and 2 port brake from factory)
With 250gr Hornady, S&B and PPU BTHP it puts the rounds pretty much in the same hole at 100yds, so I will say there has to be something wrong with your barrel or rifle
